|July 22||Company A organized as 1st Company New Hampshire Heavy Artillery and mustered in. Stationed at Fort Constitution|
|September 17||Company B organized as 2nd Company New Hampshire Heavy Artillery and mustered in. Stationed at Fort McClary, Kittery Point|
|May 6||Companies A and B ordered to Washington, D.C. Attached to Augur’s Command, Defenses of Washington, 22nd Corps, and assigned to duty in the Defenses of Washington, D.C.
Company A at Forts Slocum, Stevens, Totten, Sumner and Batteries Cameron, Parrott, Kendall and Vermont. Company B at Forts Bunker Hill, Saratoga, Lincoln, Bayard, Gaines and Foote.
|July 11-12||Companies A and B repulse Early’s attack on Washington|
|September 2 – October 17||Companies C – L organized and ordered to Washington, D.C., as soon as organized for duty in the Defenses of the city|
|November 5||Company “M” formed by assignment of 1st New Hampshire Battery, Volunteer Light Artillery but remained detached as a Light Battery.|
|November 25||Company A ordered to Portsmouth Harbor|
|June||Regiment mustered out. Recruits consolidated to 2 Companies|
|February||Company B ordered to Portsmouth Harbor, N.H.|
|September 11||Recruits mustered out|